The present invention relates generally to a wireless polymeric twist tie. More particularly, the present invention relates to a wireless polymeric twist tie formed from a polycarbonate alloy.
Twist ties are used for various fastening and closing purposes. Typically, twist ties are used to seal a package having an open end, such as a bag. To seal the package, packaging material adjacent to the open end is gathered. The twist tie is extended around the gathered packaging material until end portions of the twist tie are adjacent to each other. The end portions are then twisted relative to the remainder of the twist tie to fasten the twist tie onto the package.
Twist ties typically include a wire that is enclosed in a paper or plastic wing. Twist ties that include the paper or plastic enclosed wire are subsequently referred to as wire twist ties. Wire twist ties have many advantageous properties that have led to widespread use of wire twist ties. For example, wire twist ties are readily applied using either manual or high speed mechanical operations. In addition, multiple fastening and unfastening cycles do not significantly affect the fastening capability of wire twist ties. Wire twist ties are also functional over a wide range of temperatures without a significant reduction in fastening capability.
There are many food packaging applications where wire twist ties play an important role because wire twist ties enable consumers to quickly access and reseal a product container numerous times. One disadvantage of existing wire twist ties is that consumers desire food to be packaged in a material that enables heating of the food in its original packaging. One type of heating where it is particularly desirable to heat food in its original packaging is in a microwave oven. Existing wire twist ties, however, are not suitable for use in microwave ovens because wire twist ties generally cause undesirable arcing when the twist tie is subjected to microwave radiation at an intensity conventionally found in microwave ovens.
Another disadvantage of existing wire twist ties concerns conventional food distribution. When food is commercially packaged for distribution to the public, it is desirable to insure that the food is free from contamination by foreign objects. Therefore, commercially packaged food is typically inspected after the food is package. A common method of inspecting food products involves the use of metal detectors. One drawback of using wire twist ties is that wire twist ties preclude the use of metal detectors.
To overcome these difficulties, a variety of non-metallic closures, such as polymeric closures have been developed. Polymeric twist ties are an example of the polymeric closures. There have been numerous attempts to develop a polymeric twist tie that exhibits desirable toughness and flexibility characteristics while also being easily fastenable and unfastenable over numerous cycles.
For example, Feltman, U.S. Pat. No. 5,607,748, which is assigned to the assignee of the present application, describes forming wireless polymeric twist ties that exhibit a tensile strength and a yield strength of greater than 9,000 psi Stolk et al., U.S. Pat. No. 4,797,313, discloses using polymeric materials that provide a yield stress of less than 9,000 psi and preferably between 2,000 and 4,000 psi. Stolk et al. indicates that a yield stress of less than 9,000 psi is necessary so that the polymeric materials exhibit a desired glass/rubber transition behavior.
There have been numerous other attempts to provide an entirely polymeric closure. For example, Thomas, U.S. Pat. No. 3,535,746; Moon, U.S. Pat. No. 3,604,066; and Hoard, U.S. Pat. No. 3,945,086, disclose polymeric closure devices. However, none of these polymeric closure devices are believed to be suitable for substitution in place of wire twist ties in machinery that presently handles high speed mechanical packaging with wire twist ties.